cn8236 Mindspeed Technologies, cn8236 Datasheet - Page 76

• Manufacturer Part Number: cn8236
• Description: Atm Servicesar Plus With Xbr Traffic Management
• Manufacturer: Mindspeed Technologies

3.0 Host Interface
3.3 Write-only Control and Status
3.3.2 Write-only Status Queues
Table 3-3. Write-only Status Queue Variables
3-8
WRITE
READ_UD
READ
INTERVAL
UPDATE
READ_UD_PNTR
Variable
3.3.2.1 Control
3.3.2.2 Queue
Management
Variables
Current SAR position in queue
Last known host position in queue as seen by
SAR
Current host position in queue
Number of queue entries processed by host
before writing READ_UD
Number of queue entries since last write of
READ_UD
Host pointer to READ_UD
The SAR reports status to the host through write-only status queues. Both the
segmentation and reassembly coprocessors use their own format of status queue.
However, the CN8236 manages all status queues with the same algorithm.
location defined within the base table for each queue. The host must assign
word-aligned (4-byte) status queue base addresses. To support multiple clients,
the CN8236 provides 32 queues of each type. The SAR and host manage each
queue independently through queue management variables. The SAR stores its
variables in internal base table registers. The host maintains its variables in its
driver. Each queue contains a programmable number of queue entries.
Table 3-3
Figure 3-5
all of the variables described in
to the host by writing a status queue entry. After it writes the entry, the CN8236
increments its write pointer (WRITE++). This write also triggers a maskable
interrupt.
queue. The VLD bit in each queue entry enables polling. The SAR sets the VLD
bit equal to 1 when it writes a status queue entry. The host resets it to 0 after
processing an entry.
These queues reside in host memory, or optionally SAR-shared memory, at a
The SAR maintains its own write pointer, WRITE. The CN8236 reports status
The host either responds to this interrupt, or periodically polls the status
Mindspeed Technologies
describes the variables for write-only status queue management.
illustrates the status queue management algorithm. The host initializes
Definition
ATM ServiceSAR Plus with xBR Traffic Management
Table
3-3.
™
sar base table
SAR Base table
Host Variable
Host Variable
Host Variable
Host Variable
Location
28236-DSH-001-B
Initialization
Host defined
&READ_UD
0
0
0
0
CN8236